1. Field of the Invention
The invention relates to a wireless communication system and a method of conducting wireless communication both of which allow a terminal device to make IP communication.
2. Description of the Related Art
As Internet has been widely utilized, there is a need to a communication system in which for instance, a terminal device mounted in an automobile can readily makes access to Internet.
Conventionally, in order to cause a terminal device mounted in an automobile to make access to Internet, the terminal device had to be connected to a cellular phone to make access to a router or a server (an access point) through which the cellular phone can make access to Internet through a cellular phone network.
However, the above-mentioned conventional way in which a terminal device makes access to an access point through a cellular phone network is not suitable for long time use, because a communication fee is unavoidably expensive.
If a user were driving an automobile, he/she would like to receive information about road traffic and/or navigation for arriving at his/her destination.
As a system for allowing a terminal device mounted in an automobile to make wireless communication therewith, a wireless system between a road and an automobile is presently developed. An example of such a wireless system is a system for automatically charging an automobile for a toll road fee. In the wireless system between a road and an automobile, a wireless communication device is mounted in an automobile, and a base station which can make wireless communication within a relatively narrow area is located around a tollbooth for transmitting information about a fee to automobile drivers. The wireless system is expected to further provide automobile drivers with various services including traffic information, by increasing the number of base stations.
However, since the above-mentioned wireless system is originally developed for the system for automatically charging an automobile for a toll road fee, the wireless system is designed not to have a network layer. Accordingly, the above-mentioned wireless system is accompanied with a problem that it is quite difficult or almost impossible to successively transmit IP packets to a terminal device now moving, from a plurality of base stations.
For instance, Japanese Unexamined Patent Publication No. 2000-4468 has suggested a wireless communication system in which a road and an automobile make interactive wireless communication with each other. The automobile has a wireless communication device for making wireless communication with the road. The road includes first means for detecting an automobile entering a service area covered with a plurality of micro-cells, and transmitting a detection signal, second means for receiving the detection signal and transmitting a first signal indicative of where the automobile is, a plurality of base stations each of which makes wireless communication with the wireless communication device and is associated with each of the micro-cells, and a controller which produces registration data of the automobile, based on the detection signal, transmits the registration data to the wireless communication device through the first means, and controls the base stations by switching the micro-cells, based on the first signal and the registration data.
The above-mentioned problem remains unsolved even in the above-mentioned Publication.